Fire a stream of alpha particles at a gold film so thin it is almost transparent. Most sail straight through, but a rare few ricochet right back, as if they had struck something tiny, hard and hidden.
When alpha particles are fired at thin gold foil, most pass straight through, a few are deflected, and very few bounce back. This shows the atom is mostly empty space with a tiny, dense, positively charged nucleus that holds most of the mass.
In the alpha-scattering experiment, alpha particles are fired at thin gold foil. Most pass straight through, a few are deflected, and a very few bounce back.
A few deflected → positive nucleus. Very few bounce back → nucleus is tiny, dense and holds the mass.
Fire alpha particles at the foil and see how most pass through while a rare few rebound.
Four quick checks. Each correct answer earns XP and lights this skill on your star map.
In the alpha-scattering experiment, most alpha particles...
The few alpha particles that are deflected show that the nucleus is...
The very few alpha particles that bounce back show that the nucleus is...
Overall, the experiment shows that the atom is...
Each observation points to a feature of the atom.
| Observation | What it shows |
|---|---|
| Most pass straight through | The atom is mostly empty space |
| A few are deflected | The nucleus is positively charged (it repels the positive alpha) |
| Very few bounce straight back | The nucleus is tiny, dense and holds most of the mass |
The rare alpha particles that bounce almost straight back are the key evidence. They show the positive charge and the mass are concentrated in a tiny nucleus, not spread thinly across the whole atom.
Unlocks once the four checks above are done. Worth more XP, written in the style of Paper 2.
Why is it significant that a very small number of alpha particles bounced almost straight back?
That most alpha particles passed straight through the foil shows that...
An alpha particle is deflected through a large angle because it...
The alpha-scattering evidence is mapped. Keep the chain going.